1. The Field of the Invention
This invention has applications in high speed transmitters deployed in optical fiber-based communications systems.
2. The Relevant Technology
Laser transmitters have recently been developed in which a laser, such as a distributed feedback (DFB) laser, is directly modulated to produce adiabatically chirped pulses. The pulses are passed through an optical discriminator or ‘optical spectrum reshaper’ (OSR) that converts the adiabatically chirped pulses into pulses having an increased amplitude modulation and extinction ratio. In some systems, the OSR also performs a pulse shaping function.
In such systems, it is important that the laser frequency be aligned with respect to the transmission spectrum of the OSR. This is generally implemented by a control loop that compares the average optical power before and after the OSR component. The control loop maintains the DFB laser wavelength at a calibrated set point by continuously adjusting the DFB laser temperature via a thermoelectric cooler (TEC).
In some transmitters, the output of the laser and the amount of light reflected back from the OSR are measured to evaluate alignment of the laser frequency with respect to the OSR. It is therefore important that the frequency response of the OSR be maintained constant in order to provide an accurate reference for controlling the frequency of the laser.
In view of the foregoing it would be an advancement in the art to provide a system and method for stabilizing the frequency response of an OSR.